Scientists have found a gene that links thickness of the brain’s gray matter and intelligence. The find could open the door to understanding why some people have learning problems – and even give an insight into psychiatric disorders.

Researchers at King’s College London have discovered a gene
that draws a link between the thickness of gray matter in the
brain and a person’s level of intelligence. The findings of the
research were published in the scientific journal Molecular
Psychiatry on Tuesday.

The gray matter itself plays an important role in perceptual
awareness, language and consciousness. Prior to this study,
scientists had already found a correlation between the thickness
of gray matter and an individual’s intelligence, but no genes had
been discovered.

The scientists examined brain scans from over 1,500 14-year-olds,
looking closely at the outermost layer of the brain, the cerebral
cortex. They also took samples of participants’ DNA and then
tested their levels of verbal and non-verbal intelligence.

“We wanted to find out how structural differences in the
brain relate to differences in the intellectual ability,”
said Sylvane Desrivieres, lead author of the study. “The
genetic variation we identified is linked to synaptic plasticity
– how neurons communicate.”

After looking at over 54,000 genetic variations associated with
the make-up of the brain, they discovered that participants
carrying a particular gene were more likely to have a thinner
cortex in the left cerebral hemisphere. These participants did
not perform as well in the intellectual tests as those who had
thicker cerebral cortexes.

The scientists identified the gene encoding a protein that
affects how brain cells communicate as the NPTN gene. Researchers
confirmed the gene’s effect by testing it on a mouse and human
brain cells in the lab, where they observed different levels of
activity in the left and right hemispheres of the brain.

Desrivieres said that the research did not amount to a discovery
of “a gene for intelligence.”

“The gene we identified only explains a tiny proportion of
the differences in intellectual ability," she said.

The new discoveries will be invaluable, however, in understanding
the biology that leads to psychiatric disorders such as
schizophrenia and autism.

"This may help us understand what happens at a neuronal level
in certain forms of intellectual impairments, where the ability
of the neurons to communicate effectively is somehow
compromised,” Desrivieres said.